Skepticon likes to tantalize you, dribbling out speaker names a few at a time. Last week they told us that Aron Ra, Amanda Knief (who has a new book out, with Barry Lynn: The Citizen Lobbyist
As I mentioned yesterday, Skepticon is the high energy fun con of the year. You should go. You should especially go if you want to learn how to put together a well-managed, exciting con on a budget — I’d like to see more of these things spring up all over the country.
But no way near as fancy and famous as TAM, of course. Only TAM manages to get the real good speakers.
/snark
So who are these boring old drones you’re talking about? Is Pat Robertson attending?
I may have to go.
If it helps, this boring old drone already has his talk subject picked out: I’m going to be discussing the Cambrian Explosion, since it seems to be the emerging cause of the year for the creationists.
@ ^ PZ Myers : isn’t that, um, a bit old news for them? I mean to talk about the Cambrian means talking about well, *millions* of years of Earth history. Like 500 plus million years ago.
Does that not automatically mean they lose – even in their minds?
(Ah, the Cambrian when the Sun was young and faint, the Moon so much closer in the sky and Earth was one big snowball with oceans of icy slush.The memories, er, was I that really old again or am I exaggerating my age ju-ust slightly?)
How come my IP is blocked by the Skepticon site?
The Cambrian was about 485 to 541 million years ago, about 1/9 to 1/8 the present age of the Earth.
The Earth’s rotation and Moon’s revolution in the Cambrian:
1 Earth year ~ 400 days and 14.1 sidereal months (present: 365.24, 13.37)
1 day ~ 22 hours
Moon’s distance ~ 0.97 * present-day value
But we could have had a 13-month calendar.
http://isotope.colorado.edu/~geol5700/Williams_2000.pdf
Faint young Sun problem: Sun’s luminosity approximated by
L/L0 ~ 1/(1 + (2/5)*(1 – t/t0))
for present-day L0 and t0 and age t
Sun’s luminosity about 0.96 the present-day value
http://arxiv.org/abs/1204.4449
As to the Earth being “one big snowball with oceans of icy slush”, that was well before the Cambrian, around 750 to 650 million years ago. Between this “snowball Earth” and the Cambrian was the Ediacaran, with its odd fossils.
“Where was everybody?” is a very interesting exercise.
http://www.scotese.com/ and http://www2.nau.edu/rcb7/ have some nice maps of continental drift since the late Precambrian. http://www2.nau.edu/rcb7/nam.html goes into detail about North America over that time.
Back in the Cambrian, the present west coast of North American did not exist. That’s most of California, Oregon, Washington, and western British Columbia. They formed from island arcs plowed up by North America from the mid Paleozoic to the Mesozoic. Most of the east coast did, however, though Florida was part of Gondwana back then, wedged between what would become South America and west Africa.
North America was near the equator then, and rotated about 90d clockwise relative to its present orientation. In the later part of the Cambrian, much of it was underwater, making huge continental shelves.
Now to the Earth’s biota.
Plants started to grow on land about 475 million years ago, in the early Ordovician: BBC – Earth News – Fossils of earliest land plants discovered in Argentina They were early liverworts, a primitive sort of land plant.
Multicellular algae go back further, with the oldest unambiguous one so far being the red alga Bangiomorpha pubescens of 1.2 billion years ago, twice as old as the base of the Cambrian.
But animals are what gets the most interest, and creationists sometimes seem to imply that the Cambrian ones were much like their present descendants and successor. But they weren’t.
Vertebrates? Proto-fish back then.
Arthropods? Not much limb specialization, mostly in the head, something like present-day centipedes and millipedes. Several arthropods back then had big front limbs, “great appendages”, something lacking from most of their successors.
Mollusks? Ancestors of gastropods, bivalves, cephalopods, and others had diverged in the Cambrian or a little before. Kimberella, in the Ediacaran, looks something like a mollusk.
Etc.